Initialize SELECT-OPTIONS values

Hi all,

i would like to initialize a parameter of my SELECT-OPTIONS.

My code :

SELECT-OPTIONS: s_date FOR sy-datum,

ptype FOR l_bkpf-blart,

pexo FOR l_bkpf-gjahr.

INITIALIZATION.

pexo-sign = 'I'.

pexo-option = 'EQ'.

pexo-high = sy-datum(4).

pexo-low = sy-datum(4) - 1.

APPEND pexo.

START-OF-SELECTION.

...

Well, my problem is that in my START-OF-SELECTION the pexo variable have not the values of INITIALIZATION, the system write in option 'BT'. Any ideas ?

Thanks